The present invention relates to a ball joint assembly, and more particularly, to a ball joint assembly utilizing a one piece semi-rigid, plastic socket member for use in connecting a windshield wiper transmission linkage for motor vehicles where substantial pivotal and canting movement occurs.
Ball socket members of plastic material are known in the prior art. Examples of such ball socket members for a windshield wiper transmission linkages are disclosed in U.S. Pat. Nos. 3,749,431, 3,845,998 and 3,853,414. In these known ball socket bushings either no seal is provided for retaining lubricant and preventing entrance of contaminants or a lip type seal integral with the ball socket is provided to effect a seal by engaging against a portion of the ball stud. In these prior art bushings, to effect a good sealing engagement the bushing must be formed of yieldable elastomer, as for example, polyurathane. Due to the severe multi-directional forces applied in a windshield wiper linkage a highly yieldable bushing results in excessive movement at the joints. Such excessive movement can produce distortion of the normal wiping pattern and cause the blade to overrun the molding about the windshield. It is therefore advantageous that a strong, rigid socket member be utilized. Since a multiplicity of linkage members and joints are used in these linkages it is advantageous for economy purposes to utilize a socket member of one size and design for the entire linkage system. This presents a problem because of design and cost considerations. Metals of different thicknesses in the various linkage members are employed depending upon space and design requirements. The socket members may be pre-lubricated. Use of a semi-rigid material in known socket members can cause fracturing during assembly due to pressure created by the entrapment of excess grease.